Oil well drilling operations usually involve rotating a string of drill pipe composed of individual sections called "joints," each typically 30 feet in length, which carries a drill bit assembly at its lower end. As the bit bores deeper into the earth, additional joints of pipe are added to the string (see A Primer of Oilwell Drilling, (1979) Petroleum Extension Service, University of Texas, Austin, Pub., 1979, incorporated herein by reference).
The "top drive" is a relatively recent development in mechanisms for rotating a drill pipe string that has gained widespread acceptance in the oil and gas drilling industry. A top drive drilling mechanism and ancillary equipment are supported by and below the traveling block of a drilling rig. The traveling block provides for moving the top drive vertically along the well bore axis to enable connecting it to the drill string. The top drive mechanism includes a drive mechanism which turns a coupling to which the upper end of the pipe string can be connected. Top drive drilling procedures eliminate the need for the long "kelly joint" previously used for connecting a drive mechanism to a drill pipe string, and the need for disconnecting the kelly joint from the drill string each time it is necessary to add or remove a single section from the drill string. Also, use of a top drive permits drill pipe to be added to the drill string in multi-joint "stands" of two or three sections of drill pipe at a time, with a corresponding reduction in time wasted and man hours expended by not having to cease drilling as often to add drill pipe.
The mouse-hole and the rat-hole are rig features previously developed in connection with rotary table drilling rigs. A mouse-hole is a substantially vertical tubular sleeve extending below the drilling rig floor with its upper opening adjacent the drill bore. The mouse-hole is used to hold the next joint of drill pipe which is to be added to the drill string. The rat-hole is a somewhat larger diameter (and often longer) tubular sleeve also located in the drilling rig floor and serves as a receptacle for the kelly.
To realize the advantages obtainable with top drive systems, it is desirable to make-up stands of drill pipe while drilling operations are in progress. However, for a variety of reasons, the task of making up multiple stands of up to three sections of drill pipe often cannot be completed fast enough to keep up with drilling operations. Consequently, the maximum efficiencies possible from use of top drive drill procedures are not always obtained. Therefore, an important step in a top drive drilling procedure is the make up or connection of one pipe joint to another, in advance.
A problem attendant with this step is the need to insure the application of the proper amount of torque to the ends of the joints being connected. Usually, torque is measured only overall, when the multi-joint stand is attached to the top drive unit, in which case, there is no measurement or control of torque at each connection between joints in the stand.
Another problem commonly encountered when making up "double" and "thribble" (as they are called in the art) stands for top drive drilling is to ensure proper alignment of the "tool joint" ends. Each section of drill pipe has an externally threaded coupling at one end, called a "pin", and at the other end, an internally threaded coupling called a "box." Drill strings typically are assembled with each joint in the string joint disposed pin end down. Misalignment of the pin and box ends of adjacent joints can slow the task of making up a stand and can lead to galling or other thread mutilation conditions.
Some top drive drilling procedures actually require the use of the top drive in the make up of joint stands. Those types of procedures that require participation of the top drive in operations other than drilling may not be making full use of the advantages top drive drilling is now recognized as offering the industry.
A need exists in the industry for alternatives and improvements in the procedures and equipment available in top drive drill rigs to enable more rapid assembly of multi-joint stands of drill pipe, while drilling operations are concurrently proceeding. Such improvements desirably should include procedures and devices for (1) accurately and efficiently aligning the pin and box ends of two joints to be connected, (2) threading those joints together (or unthreading them for breakout), (3) applying a determined amount of torque to finish the connection (or break the connection for a backout), and (4) not requiring participation of the top drive to accomplish any of the make up operations. Further, the equipment should be flexible for use with existing drill rig arrangements and procedures to reduce the need for retraining of rig personnel.
The recognized advantages of top drive drilling in fact have motivated the industry to develop innovative technologies and improvements which support or attempt to optimize those advantages. Specifically, the advantage of being able to attach to the drill string multiple sections of drill pipe at-a-time has led to the development of new devices and methods for making up and breaking out multi-joint drill pipe stands.
Kennard (U.S. Pat. No. 3,293,959) discloses a device mounted over the rat-hole on a drilling platform. Kennard describes using a kelly joint for rotation, a housing and means for supporting a length of pipe to be added to the drill string, and clamping means for preventing the pipe from rotation during make-up with the kelly joint. The housing is mounted on spring legs to resiliently support and upwardly bias the joint to be made up relative to the kelly joint. A winch having a cable and stabbing hook swings the kelly joint into position over the housing and vertically aligns it with the pipe joint supported by the housing.
Stogner et al. (U.S. Pat. No. 5,351,767, herein incorporated by reference) teach an apparatus and method where multi-joint stands of drill pipe are made up and broken out in a drilling rig using a rig's mouse-hole feature. In Stogner et al., make up and break out are accomplished by using a powered mouse-hole to rotate a lower joint of pipe relative to an upper joint, which is held in alignment and prevented from rotating by tong assembly. However, this apparatus and method do not accomplish the controlled torquing of each connection between joints in a stand.
Additionally, Stogner et al. describe a rotating mouse-hole tool for use with a standard mouse-hole in situations where the drilling rig does not have a powered mouse-hole available. The rotating mouse-hole tool itself provides the rotational force for threading and unthreading joint of drill pipe. The rotating mouse-hole tool of Stogner et al. is to be used with a particular type of drill pipe that has a neck formed by increasing the diameter of the coupling end of the pipe (described in Stogner et al. as known in the art as "a tool joint box").
The PHANTOM MOUSE.RTM. (International Tool Co., Ltd., Houston, Tex.) is a commercially available example of a rotating mouse-hole tool for tool joint make up and break out. However, rotating mouse-hole tools generally do not make up the joint connection to full torque, and a stand of pipe is tightened to full make up torque only after it is inserted into the drill string by means of the top drive. Make up torque is applied overall to the stand, not individually to each connection. This procedure consumes top drive operating time and can result in variation in the make up torque of individual connections in stands of more than two sections of drill pipe, or in the connection of the stand to the drill string. Another limitation of the rotating mouse-hole tool is that it is not easily usable on drill string.